The present invention relates to a method to plate an article which has a portion to be nonplated at a high speed, the remainder being plated completely. The present invention also relates to an apparatus which is able to plate an article having a portion of nonplating at a high speed. Particularly the present invention is useful when applied to a housing with an earth electrode for spark plugs for internal combustion engines.
Conventionally, a spark plug housing made of ferrous metal with an earth electrode made of Ni-Cr (Nickel-Chromium) alloy has been plated in a barrel which holds a lot of housings, or by hanging a lot of housings on a plating hanger, which is the same as the conventional method for other general articles.
However in the method above, the plating is made on such a portion that needs no plating from the beginning or the portion that is difficult to plate because of the base metal of Ni-Cr alloy, i.e. the earth electrode. Therefore when the earth electrode is bent to make the final product, the plating is sometimes peeled off, or a similar problem occurs when the spark plug is mounted to the engine and subjected to severe heat cycle to cause sometimes a bridge between the earth and center electrodes.
Therefore the inventors have adopted in their factory, which is not open to the public, a masking member or masking paint for the earth electrode of the spark plug housing, thereby giving no plating to the earth electrode. However, it took a lot of time, long and complicated processes and much work force.